When a power supply is switched on, the output voltage level of the power supply rises from zero volts to the nominal supply voltage, which may be, for example, 3.3 volts or 5.0 volts. To better ensure proper operation of an integrated circuit that is powered by the power supply, "power-on" detection circuits are used to prevent the integrated circuit from performing logical operations until the supply output voltage has achieved a predetermined level.
Different power supplies require different amounts of time to rise or "ramp" to the nominal supply voltage, and the power-on detection circuit of an integrated circuit should be able to function accurately over a wide range of ramp rates to better ensure proper operation regardless of the power supply used by a particular system. Therefore, it is desirable to provide a power-on detection circuit that operates over a wide range of ramp rates.